This paper presents a study of the dielectric properties of ZnNb2O6 (ZNO) with added CaTiO3 (CTO) in the microwave (MW) region. An X-ray diffraction analysis is performed, and a reaction between ZNO and CTO is demonstrated that results in the formation of other crystalline phases. The dielectric properties in the MW region show no significant change in permittivity (ε'r), whereas the addition of CTO results in an increase in the dielectric loss (tan δ). The thermal stability is also measured, and the temperature coefficient of resonant frequency (τf) is varied from −88.95 to −8.16 ppm °C−1. Numerical simulations are carried out to evaluate these materials for use as a dielectric resonator antenna, and the results show a reflection coefficient (|S11|) of below −10 dB, a radiation efficiency above 96 %, a bandwidth ranging from 100 to 170 MHz, and a gain of above 4.50 dBi. The values obtained here show that these materials could be employed in electronic devices acting in the C- and S-bands.